1. Field of the Invention
The present invention relates to a method of making hydroxymethylphosphonates, polyurethane foam-forming compositions containing the same, polyurethane foam formed from the polyurethane foam-forming compositions, and polyurethane foam articles made therefrom.
2. Description of Related Art
Polyurethanes are materials that are suitable for a large number of different applications in the industrial and private sectors. However, their use presents problems whenever it is involved in areas where there is a risk of fire. To modify their fire behavior, flame-retarding agents are usually added to these polyurethane materials.
Phosphorus compounds are highly effective flame-retarding agents for polyurethane foam, owing to their high phosphorous content and good compatibility with polyurethane systems. Unfortunately, various phosphorus-based flame retardants have various processing problems associated with their use. Hydroxymethylphosphonates have found some use as flame-retarding agents but their use has been severely limited by their problematic synthesis, low purity, and specifically their content of acidic by-products and water. Further, the formation of hydroxymethylphosphonates has previously been conducted very quickly, and in small batches, due to extreme exotherms, which occur in the production of such hydroxymethylphosphonates, which exotherms can result in high acid content. Other attempts to produce hydroxymethylphosphonates have necessitated extremely high reaction temperatures. Still other attempts to produce hydroxymethylphosphonates have resulted in significant byproducts and/or low product yields. Therefore, there is a need for a means of making hydroxymethylphosphonates, which avoids these quality and processing difficulties.